Adjustment for the magnets in telephone receivers and the like



April 27 1926.

A. H. MIDGLEY ADJUSTMENT FOR THE MAGNETS IN TELEPHONE RECEIVERS AND THELIKE Filed August 25 1925 Patented 7 Apr. 27, 1926.

UNITED? STATES ALBERT HENRY MIDGLEY -OF uxnnreen, ENGLAND.

ADJUSTMENT FOR THE'MAGNE T S IN TELEPHONEiREGEIVERSAND THE LIKE.-

Application filed Ai1gust-25, 1925. Serial N0. 52,432.

To all'wlwmz't may concern. I 7 I Be it known that I, ALBERT HENRY MIDG-LEY, a subject of the King of Great. Britain,

residing at F airfield, Hareiield Road; UX

bridge, in thecounty 01 Middlesex, England,

have invented certain new and useful Improvements in and Connected withAdjustments for the Magnets in Telephone Receivers and the like, ofwhich the following is a specification. i

This invention comprises improvementsin and connected with adjustmentsfor the magnets of telephone receiver's, loud speakers and the like andis concerned with, arrangements in which the permanent-magnet issupported by pivots about which it is adjusted bymeaus such as a screwforgiving an accurate adjustment of the pole tipsin relation to'thevibratory diaphragmor the like. In known arrangements the pole pieceshave been carried at the freev ends oflimbs of a horse-shoe magnetsupported pivotally at the opposite ends oi" the'limbs. In sucharrangements the flux between the pole tips was parallel withthe'pivotal axis. l/Vhen the 'faees'of the pole tips are parallel withthe diaphragm there is a magnetic flux which'is'unitorm over the'facesof the pole tips and the opposed portions oi. the diaphragm but when'themagnet is pivotally adjusted so that the said faces are no longerparallel with the diaphragm but inclined thereto; a crowding of thelines offorce takes place in those portions of the pole faces which lienearer. to the diaphragm than others. In this way the incidence and thedistribution of the magnetic flux is altered in performing the pivotaladjustment.

Now according to this invention, a pivotally supported telephone magnetstructure has the pole pieces disposed in such a man- 'ner that thedirection of the flu); is at right angles to the pivotal axis and in thedirection of the length ofthe magnet. With such an arrangement, thedistribution of the flux remains about the same in spite of the factthat in the pivotal adjustment of the mag net, that pole piece which isfarther from the pivot moves over a greater distance than the pole piecewhich is nearer to the pivot.

In order to enable the invention" to be readilyunderstood, referenceisinade to the accompanying drawing illustrating one suitableconstruction in accordance with these improvements in which drawingsvibratory diaphragm Z) in operative relation with magnet poles c, thediaphragm I) being coveredby a cap or cover (Z provided with'a snigot, cfor'the fitting on of ahorn or trumpet (not shown). which maybe of anysuitable form.

The magnet structure comprises a pair of permanent bar magnets mwhichare braced apart by stout yoke pieces n it these bars and y'olresbe'ingheld' strongly together by means of bolts andnuts at'0 aud o, Thepole pieces 0" are seci'ir'ed against; the inner ends of the yokes n nby wedging means p which'are not further described herein as they formno part of this invention but are fully described and claimed in mypatent application of even date. The magnet structure possesses strengthand rigidity suiting'it for thepivotal mounting now described; Also itwill be seen that the yokes 41,42 are spaced apart-inthe lengthdirection of the magnet structure.

At one end of the structure, the bar magnets are' fitted with centrepoint bearings. For'example, the ends of the belt at 0 may be formed.with conical depressions or centres which are adapted for being engagedby centre point screws 9 screwed into the cast framing 1" secured withinthe base a, these screws q being adjusted so that their points engagepivotally with the centre point F'gure l is a central vertical sectionof bearing recesses aforesaid. The yoke piece n is prolonged beyond theends of the bar magnets m and such prolongation .9 may be of reducedthickness as shown. The prolongation s extends beneath a part of thecasting 1 and rests upon a bow or blade spring t this spring beingsupported by adjustable nuts u screwing on screws '0 inserted from abovethrough holes in the cover (Z and casting r. The spring t is slottedwhere it takes over the screws '0 as shown in'Figure 3, in order that itmay be free to flex under different degrees of, adjustment pressure. Anadjusting screw to provided with a milled head is screwed down throughthe casting 1" and so as to bear upon the top surface of theprolongation s of the yoke piece it. By screwing down the screw w themagnet structure is depressed about its pivots Q against the resistanceof the spring t and the pole tips 0 are adjusted away from the diaphragmor the like. Upon unscrewing the screw to the spring t or otherresilient support elevates the magnet structure about the pivots g andthe pole tips are adjusted towards the diaphragm Z), as will be readilyunderstood.

Referring to Figure 1, it will be seen that when the screw 10 is screweddown to depress the right hand end of the magnet structure, the gapbetween the tip of the right hand pole piece a and the diaphragm will beincreased to a greater extent than the gap between the tip ofthelefthand pole piece 0 and the diaphragm. However, it will be apparent thatsuch alteration of the gaps will simply increase the reluctance of themagnetic circuit without substantially altering the distribution of thelines of force flowing through the diaphragm.

The casting" 1" may be a die casting in aluminum alloy or the likesecured down upon the base a principally by means of screw and nuts w.The milled head of the adjusting screw to being situated at the top andat the periphery of the cover cl, it is very conveniently situated forinstant operation and the adjustments can therefore be performed withmuch greater nicety and freedom tha-n'is possible when the head of theadjusting screw is situated beneath the base or at the back of a loudspeaker. Furthermore, the terminals y, y for the magnet coils may be onthe top of the cover cl so as to be readily accessible,as will beapparent from the drawing.

The hereinbefore described magnet structure is not the only suitablestructure for the purpose of this invention, andthe means for pivotallymounting and adjusting it can be varied without departing from theseimprovements.

I claim 1. Telephonic receiver comprising an elongated magnet structure,a pivot axis for said structure at one end thereof; pole pieces securedin said structure at about the middle of its length and arranged onebehind the other along a line perpendicular to the pivot axis, andadjusting means operative directly upon the free end of the structure toadjust the latter about said axis.

2. Telephonic receiver comprising an adjustable magnet structurecomposed of parallel barmagnets, yoke pieces spacing said bar magnetsand pole pieces secured between said yoke pieces and against the innerends thereof. 7 7 f 3. Telephone receiver. comprising a magnet structurecomposed of parallel bar magnets and yoke pieces inserted as spacersbetween the end portions of said bar magnets,

transverse securing bolts bolting together said bar magnets and yokepieces, one of said bolts being adapted as an antifriction pivotbearing, and pole pieces secured against the inner ends of respectiveyoke pieces substantially asset fort i 4. Telephone magnet structurecomprising a frame having permanent bar magnets for its longitudinalside members and yoke pieces spa-cingsaid bar magnets for its endmembers, polar formations on the inner ends of the yoke pieces, and polepieces perpendicular to the plane of said frame and secured againstrespective polar formations.

5. Telephone receiver comprising a magnet structure composed of parallelbar magnets spaced apart by yoke pieces disposed between the endport-ions of said bar mag nets, a pivotal support for one end of saidstructure, a resilient support for the opposite end of saidstructure,mechanical adjusting means operative in opposition to said resilientmeans, and pole pieces secured in said structure against the inner endsof respective yoke pieces. v

6. Telephone receiver comprising a magnet structure composed of parallelbar mag nets spaced apart by yoke piecesdisposed between end portions ofsaid bar magnets, a pivot support for one end of said structure, anadjustable spring support for the opposite end of said structure,mechanical adjusting means operative upon said structure in oppositionto said spring, and pole pieces secured in said structure in contactwith respective yoke pieces substantially as set fortl.

7. Telephone receiver comprising a magnet structure composed of parallelbar magnets spaced apart by yoke pieces disposed between end portions ofsaid bar magnets, a pivot support for one end of said structure, a bowspring engaging beneath the opposite end of said structure, adjustablesupports for the ends ofv said bow spring, an adjusting screw operablefrom above and acting downwardly on said structure against theresistance of saidspring, and pole pieces secured in said structure incontact with re spective yoke pieces substantially as set forth.

8. In atelephone receiver a robust magnet structure comprising permanentbar magnets as longitudinal side members and yoke pieces inserted asspacers between end portions of said bar magnets. said bar magnets andyoke pieces being strongly bolted together, pole pieces in longitudinalalign- 10 the opposite end of said frame, substantially as set forth.

ALBERT HENRY MIDGLEY.

